Durable CO2 conversion in the proton-exchange membrane system.

Electrolysis that reduces carbon dioxide (CO2) to useful chemicals can, in principle, contribute to a more sustainable and carbon-neutral future1-6. However, it remains challenging to develop this into a robust process because efficient conversion typically requires alkaline conditions in which CO2 precipitates as carbonate, and this limits carbon utilization and the stability of the system7-12. Strategies such as physical washing, pulsed operation and the use of dipolar membranes can partially alleviate these problems but do not fully resolve them11,13-15. CO2 electrolysis in acid electrolyte, where carbonate does not form, has therefore been explored as an ultimately more workable solution16-18. Herein we develop a proton-exchange membrane system that reduces CO2 to formic acid at a catalyst that is derived from waste lead-acid batteries and in which a lattice carbon activation mechanism contributes. When coupling CO2 reduction with hydrogen oxidation, formic acid is produced with over 93% Faradaic efficiency. The system is compatible with start-up/shut-down processes, achieves nearly 91% single-pass conversion efficiency for CO2 at a current density of 600 mA cm-2 and cell voltage of 2.2 V and is shown to operate continuously for more than 5,200 h. We expect that this exceptional performance, enabled by the use of a robust and efficient catalyst, stable three-phase interface and durable membrane, will help advance the development of carbon-neutral technologies.

A High-Dimensional Atlas of Human T Cell Diversity Reveals Tissue-Specific Trafficking and Cytokine Signatures.

Depending on the tissue microenvironment, T cells can differentiate into highly diverse subsets expressing unique trafficking receptors and cytokines. Studies of human lymphocytes have primarily focused on a limited number of parameters in blood, representing an incomplete view of the human immune system. Here, we have utilized mass cytometry to simultaneously analyze T cell trafficking and functional markers across eight different human tissues, including blood, lymphoid, and non-lymphoid tissues. These data have revealed that combinatorial expression of trafficking receptors and cytokines better defines tissue specificity. Notably, we identified numerous T helper cell subsets with overlapping cytokine expression, but only specific cytokine combinations are secreted regardless of tissue type. This indicates that T cell lineages defined in mouse models cannot be clearly distinguished in humans. Overall, our data uncover a plethora of tissue immune signatures and provide a systemic map of how T cell phenotypes are altered throughout the human body.

Robust Thiazole-Linked Covalent Organic Frameworks for Water Sensing with High Selectivity and Sensitivity.

The rational design of covalent organic frameworks (COFs) with hydrochromic properties is of significant value because of the facile and rapid detection of water in diverse fields. In this report, we present a thiazole-linked COF (TZ-COF-6) sensor with a large surface area, ultrahigh stability, and excellent crystallinity. The sensor was synthesized through a simple three-component reaction involving amine, aldehyde, and sulfur. The thiazole and methoxy groups confer strong basicity to TZ-COF-6 at the nitrogen sites, making them easily protonated reversibly by water. Therefore, TZ-COF-6 displayed color change visible to the naked eye from yellow to red when protonated, along with a red shift in absorption in the ultraviolet-visible diffuse reflectance spectra (UV-vis DRS) when exposed to water. Importantly, the water-sensing process was not affected by polar organic solvents, demonstrating greater selectivity and sensitivity compared to other COF sensors. Therefore, TZ-COF-6 was used to detect trace amounts of water in organic solvents. In strong polar solvents, such as N,N-dimethyl formamide (DMF) and ethanol (EtOH), the limit of detection (LOD) for water was as low as 0.06% and 0.53%, respectively. Even after 8 months of storage and 15 cycles, TZ-COF-6 retained its original crystallinity and detection efficiency, displaying high stability and excellent cycle performance.

Mixed-Linker Strategy for the Construction of Sulfone-Containing D-A-A Covalent Organic Frameworks for Efficient Photocatalytic Hydrogen Peroxide Production.

The solar-driven photocatalytic production of hydrogen peroxide (H2O2) from water and oxygen using semiconductor catalysts offers a promising approach for converting solar energy into storable chemical energy. However, the efficiency of photocatalytic H2O2 production is often restricted by the low photo-generated charge separation, slow surface reactions and inadequate stability. Here, we developed a mixed-linker strategy to build a donor-acceptor-acceptor (D-A-A) type covalent organic framework (COF) photocatalyst, FS-OHOMe-COF. The FS-OHOMe-COF structure features extended π-π conjugation that improves charge mobility, while the introduction of sulfone units not only as active sites facilitates surface reactions with water but also bolsters stability through increased interlayer forces. The resulting FS-OHOMe-COF has a low exciton binding energy, long excited-state lifetime and high photo-stability that leads to high performance for photocatalytic H2O2 production (up to 1.0 mM h-1) with an H2O2 output of 19 mM after 72 hours of irradiation. Furthermore, the catalyst demonstrates high stability, which sustained activity over 192 hours of photocatalytic experiment.

Covalent Organic Framework Nanohydrogels.

Nanohydrogelation of covalent organic frameworks (COFs) will undoubtedly open up new applications for them in water, such as aqueous catalysis and biomedicine. It is currently a great challenge to achieve water dispersion of COFs through either bottom-up construction strategies or top-down exfoliating technologies. Herein, poly(N-isopropylacrylamide) (PNIPAM)-postmodified COF nanohydrogels (COF-NHGs) are successfully designed and synthesized via in situ atom-transfer radical polymerization (ATRP) on a scaffold of COFs. During the polymer growth process, the bulk COFs are exfoliated into nanosheets with a lateral size of ∼500 nm and a thickness of ∼6.5 nm. Moreover, their size can be precisely controlled by the degree of polymerization of PNIPAMs. In aqueous solution, the obtained COF-NHGs are assembled into nanohydrogels retaining intra-plane crystallinity and exhibit a temperature-sensitive sol-gel phase transition. With excellent solubility in organic solvents, the COF-NHGs' intrinsic physical properties in the solution state can be characterized through their solution nuclear magnetic resonance and ultraviolet absorption spectra. These results put forward new opportunities for regulating the solution processability of COFs and building an intelligent, stimuli-response platform of COF-polymer composite nanohydrogels for device applications.

Ultrathin Hollow Co/N/C Spheres from Hyper-Crosslinked Polymers by a New Universal Strategy with Boosted ORR Efficiency.

Porous carbon materials with hollow structure, on account of the extraordinary morphology, reveal fascinating prospects in lithium-ion batteries, electrocatalysis, etc. However, collapse in ultrathin carbon spheres due to insufficient rigidity in such thin materials obstructs further enhanced capability. Based on hyper-crosslinked polymers (HCPs) with sufficient pore structure and rigid framework, a new bottom-up strategy is proposed to construct SiO2 @HCPs directly from aromatic monomers. Heteroatom and function groups can be facilely introduced to the skeleton. The thickness of HCPs' wall can be tuned from 9 to 20 nm, which is much thinner than that of hollow sphere synthesized by the traditional method, and the sample with a thickness of 20 nm shows the highest surface area of 1633 m2 g-1 . The oxygen reduction reaction is conducted and the CoNHCS electrocatalysts with an ultrathin thickness of 5 nm display higher half-wave potential than those of bulk samples, even better than commercial Pt/C electrode. On account of the hollow structure, the relative current density loss of electrocatalysts is only 4.1% in comparison with 27.7% in Pt/C electrode during the 15 000 s test, indicating an obvious higher long-term stability. The new strategy to construct hollow HCPs may shed light on efficient chemical catalysis, drug delivery, and electrocatalysis.

Covalent Triazine Frameworks (CTFs): Synthesis, Crystallization, and Photocatalytic Water Splitting.

Covalent Triazine Frameworks (CTFs) have received great attention from academia owing to their unique structure characteristics such as nitrogen-rich structure, chemical stability, fully conjugated skeleton and high surface area; all these unique properties make CTFs attractive for widespread applications, especially for photocatalytic applications. In this review, we aim to provide recent advances in the CTFs preparation, and mainly focus on their photocatalytic applications. This review provides a comprehensive and systematic overview of the CTFs' synthetic methods, crystallinity lifting strategies, and their applications for photocatalytic water splitting. Firstly, a brief background including the photocatalytic water splitting and crystallinity are provided. Then, synthetic methods related to CTFs and the strategies for enhancing the crystallinity are summarized and compared. After that, the general photocatalytic mechanism and the strategies to improve the photocatalytic performance of CTFs are discussed. Finally, the perspectives and challenges of fabricating high crystalline CTFs and designing CTFs with excellent photocatalytic performance are discussed, inspiring the development of CTF materials in photocatalytic applications.

Intraprocedural, Intra-Arterial CT Foot Perfusion Examination for Assessment of Endovascular Therapy in Patients With Critical Limb Ischemia: A Prospective Pilot Study.

BACKGROUND: Current techniques to evaluate computed tomography (CT) foot perfusion in patients with critical limb ischemia use high contrast doses and cannot be used during endovascular procedures. CT perfusion of the foot with intra-arterial contrast injection during endovascular treatment in a hybrid angiography CT suite might solve these problems. PURPOSE: The main objective of this study was to evaluate whether intra-arterial CT foot perfusion using a hybrid CT angiosystem is feasible during endovascular treatment for critical limb ischemia. MATERIAL AND METHODS: This prospective pilot study investigated intraprocedural, intra-arterial CT perfusion of the foot using a hybrid CT angiosystem in 12 patients before and after endovascular treatment for critical limb ischemia. Time to peak (TTP) and arterial blood flow were measured before and after treatment and compared using a paired t test. RESULTS: All 24 CT perfusion maps could be calculated adequately. The contrast volume used for one perfusion CT scan was 4.8 ml. The mean TTP before treatment was 12.8 seconds (standard deviation [SD] 2.8) and the mean TTP posttreatment was 8.4 seconds (SD 1.7), this difference being statistically significant (p=.001). Tendency toward increased blood flow after treatment, 340 ml/min/100 ml (SD 174) vs 514 ml/min/100 ml (SD 366) was noticed (p=.104). The mean effective radiation dose was 0.145 mSv per scan. CONCLUSION: Computed tomography perfusion of the foot with low contrast dose intra-arterial contrast injection during endovascular treatment in a hybrid angiography CT suite is a feasible technique. CLINICAL IMPACT: Intra-arterial CT foot perfusion using a hybrid CT-angiography system is a feasible new technique during endovascular therapy for critical limb ischemia to assess the results of the treament. Future research is necessary in defining endpoints of endovascular treatment and establishing its role in limb salvage prognostication.

High-Suspicion Subcentimeter Thyroid Nodules: Cost Effectiveness of Active Surveillance versus Fine Needle Aspiration.

PURPOSE: To compare the cost-benefit of active surveillance (AS) against immediate fine needle aspiration (FNA) of sonographically suspicious subcentimeter thyroid nodules. MATERIALS AND METHODS: A Markov model was constructed to compare the cost-benefit of 3 strategies from the point of discovery until death: (a) Surveillance of all nodules, (b) Surveillance of nodules with positive cytology, and (c) Surgery of nodules with positive cytology. The reference case was a 40-year-old woman with a sonographically suspicious subcentimeter thyroid nodule. Transition probabilities, costs, and health state utilities were derived from the literature. Sensitivity analyses were performed to evaluate model uncertainty. Willingness-to-pay threshold was set at $100,000/quality-adjusted life year. RESULTS: Surveillance of nodules with positive cytology dominated in the reference scenario and was cost-beneficial over Surveillance of all nodules, independent of the utility of AS. Surveillance of all nodules was cost-beneficial only at a life expectancy of <2.6 years or surveillance duration of <4 years. CONCLUSIONS: While current guidelines recommend AS of sonographically suspicious subcentimeter nodules, the results of this study suggest that immediate FNA (Surveillance of nodules with positive cytology) is more cost-beneficial than AS (Surveillance of all nodules). Patients with positive cytology on FNA may subsequently opt for AS (Surveillance of nodules with positive cytology) or surgery (Surgery of nodules with positive cytology) according to their level of comfort (ie, utility) with AS.

Light Triggered Pore Size Tuning in Photoswitching Covalent Triazine Frameworks for Low Energy CO2 Capture.

Recently, photo switching porous materials have been widely reported for low energy costed CO2 capture and release via simply remoted light controlling method. However, most reported photo responsive CO2 adsorbents relied on metal organic framework (MOFs) functionalisation with photochromic moieties, and MOF adsorbents still suffered from chemically and thermally unstable issues. Thus, further metal free and highly stable organic photoresponsive adsorbents are necessary to be developed. CTFs, because of their high porosity and stability, have attracted great attention for CO2 capture. Considering the high CO2 uptake capacity and structural tunability of CTFs, it suggests high potential to fabricate the photoswitching CTF materials by the same functionalisation method as MOFs. Herein, the first series of photo switching CTFs were developed for low energy CO2 capture and release. Apart from that, the CO2 switching efficiency could be doubled either through the azobenzene numbers adjusting method or through the previously reported structural alleviation strategy. Furthermore, the pore size distribution of azobenzene functionalised PCTFs also could be tuned under UV exposure, which may contribute to the UV light induced decrease of CO2 uptake capacity. These photoswitching CTFs represented a new kind of porous polymers for low energy costed CO2 capture.

Crystalline Covalent Triazine Frameworks with Fibrous Morphology via a Low-Temperature Polycondensation of Planar Monomer.

The morphology regulation of covalent triazine frameworks (CTFs) is a great challenge, which may be due to the difficulty in controlling its morphology by traditional synthesis methods. Herein, a general approach to fabricate morphology controllable CTFs by a mild polycondensation reaction in mixed solvents without any templating agents is reported. As a proof of concept, a type of crystalline CTFs with distinctive fibrous morphology (MS-F-CTF-1) (MS: Mixed Solvent; F: Fibrous Morphology) is developed by adjusting the ratio of mixed solvents to control the solubility of monomers, so that the nucleation, crystal growth, and subsequent self-assembly are controlled, which facilitates the formation of fibrous morphology. The resultant crystalline MS-F-CTF-1 shows uniform fibrous morphology with a diameter of about 100 nm and a length of several micrometers. Notably, the fibrous morphology of CTFs can efficiently improve the photocatalytic hydrogen evolution performance, in which the hydrogen evolution rate can be boosted by about two times in comparison to block ones.

Grafting Hypercrosslinked Polymers on TiO2 Surface for Anchoring Ultrafine Pd Nanoparticles: Dramatically Enhanced Efficiency and Selectivity toward Photocatalytic Reduction of CO2 to CH4.

Metal deposition with photocatalyst is a promising way to surmount the restriction of fast e- /h+ recombination to improve the photocatalytic performance. However, the improvement remains limited by the existing strategies adopted for depositing metal particles due to the serious aggregation and large unconnected area on photocatalyst surface. Here, a strategy is proposed by directly grafting hypercrosslinked polymers (HCPs) on TiO2 surface to construct Pd-HCPs-TiO2 composite with uniform dispersion of ultrafine Pd nanoparticles on HCPs surface. This composite with surface area of 373 m2 g-1 exhibits improved photocatalytic CO2 conversion efficiency to CH4 with an evolution rate of 237.4 µmol g-1 h-1 and selectivity of more than 99.9%. The enhancement can be ascribed to the grafted porous HCPs with high surface area and N heteroatom on TiO2 surface for the stabilization of Pd nanoparticles, favoring the electron transfer and CO2 adsorption for selective CH4 production. This strategy may hold the promise for design and construction of porous organic polymer with semiconductor for efficient photocatalytic conversion.

Unprecedented Processable Hypercrosslinked Polymers with Controlled Knitting.

Processable microporous organic polymers (MOPs) attract incomparable research interest because their vairous types, such as monoliths and membranes are for practical application. Most processable MOPs usually need harsh conditions such as the use of expensive metal catalysts, specialized stereospecific monomers, etc., which restrict the sustainable and real applications of processable MOPs. Therefore, the economical mass production of processable MOPs remains a formidable challenge. Herein, a novel strategy is reported for constructing processable hypercrosslinked polymers (HCPs) need two steps synthesis of pre-crosslinking and deep-crosslinking using divinylbenzene (DVB) as a self-crosslinking monomer under the catalysis of a small amount of FeCl3 . The resulting HCPs monoliths possess high BET surface area of 1033-1056 m2 g-1 with hierarchical porosity, and show excellent mechanical strength up to 65 MPa. It is, to the best of authors' knowledge, the first report of using aromatic vinyl monomers as self-crosslinking monomers to generate HCPs monoliths with high surface area, yielding no by-products, and high mechanical strength.

Smart Synthesis of Hollow Microporous Organic Capsules with a Polyaniline Modified Shell.

In this work, novel hypercrosslinked polymer-based hollow microporous organic capsules with a polyaniline (PANI)-modified shell (PANI@S-HMOCs) are prepared by in-situ polymerization of aniline in the porous structure of the sulfonated hollow microporous organic capsules (S-HMOCs). PANI@S-HMOC1, PANI@S-HMOC2, and PANI@S-HMOC3 are made by adjusting S-HMOCs and aniline weight ratios of 4:1 and 3:1, and 2:1, respectively. The characterizations of PANI@S-HMOCs demonstrate that electrostatic interaction between aniline and sulfonic acid groups plays an important role in encapsulating PANI in the pores of the shell. The content of PANI shows an evident effect on the porosity of PANI@S-HMOCs, and an appropriate polyaniline loading amount may increase the surface area. PANI@S-HMOC1 and PANI@S-HMOC2 have higher BET surface areas (529 and 503 m2 g-1 ) than S-HMOCs (424 m2 g-1 ), but PANI@S-HMOC3 has lower BET surface area (380 m2 g-1 ). Based on the structural and textural features, PANI@S-HMOC2 shows good adsorption performance for Cr(VI) from aqueous media (156 mg g-1 , pH = 2, and 27 mg g-1 , pH = 7).

Large thyroid nodules: should size alone matter?

BACKGROUND: The management of thyroid nodules ≥ 4 cm is controversial due to conflicting evidence on the prevalence of malignancy and diagnostic accuracy of fine-needle aspiration cytology (FNAC). Some literature recommends routine excision of large thyroid nodules due to high cytology false negative rates (FNR). We aim to investigate the diagnostic accuracy of FNAC, prevalence of malignancy in large (≥ 4 cm) thyroid nodules compared to nodules < 4 cm, and the clinical and ultrasound characteristics of those large nodules with false negative cytology. METHODS: This was a retrospective case-log review in a tertiary referral hospital. All thyroid nodules subjected to Ultrasound (US)-guided FNAC by the Interventional Radiology department between December 2011 and November 2017 were included. Data on patient demographics, thyroid US features, cytology findings, and surgical histology were collected and analyzed. Sensitivity, specificity, and FNR were calculated based on FNAC results and final post-operative histology. Factors associated with a false negative result were analyzed using univariate and multivariate analyses. RESULTS: A total of 4982 nodules were studied, including 4419 < 4 cm and 563 ≥ 4 cm. Malignancy rates were similar in both groups. For nodules ≥ 4 cm, FNAC sensitivity was 40%, specificity 100%, and FNR 6.6% compared to 4.2% in nodules < 4 cm. Within malignant nodules, there was a significantly higher proportion of follicular and Hurthle cell carcinomas in nodules ≥ 4 cm. Amongst nodules ≥ 4 cm, multivariate analysis revealed male gender to be an independent predictor of FNR (OR 3.32; 95% CI 1.29-8.59). CONCLUSION: Larger nodules ≥ 4 cm have a similar malignancy rate as nodules < 4 cm, and FNAC FNR is low at 6.6%. Management of large thyroid nodules should be individualized based on their clinical, sonographic and cytological features rather than routine surgery.

Three-Dimensional Crystalline Covalent Triazine Frameworks via a Polycondensation Approach.

The growth of crystalline covalent triazine frameworks (CTFs) is still considered as a great challenge due to the less reversible covalent bonds of triazine linkages. The research studies of crystalline CTFs to date have been limited to two-dimensional (2D) structures, and the three-dimensional (3D) crystalline CTFs have never been reported before. Herein we report the design and synthesis of two 3D crystalline CTFs, termed 3D CTF-TPM and 3D CTF-TPA through a reversible/irreversible polycondensation approach. The targeted 3D CTFs adopt ctn topology, and show moderate crystallinity, relatively large surface area (ca. 2000 m2 g-1 ), and high CO2 uptake capacity (23.61 wt.%). Moreover, these 3D CTFs exhibit ultrastability in the presence of boiling water, strong acid (1 M HCl) and strong base (1 M NaOH). This contribution represents the first report of 3D crystalline CTFs, which not only extends their structural diversity but also offers a synthetic strategy and structural basis for expanding practical applications of CTF materials.

Special Report of the RSNA COVID-19 Task Force: Crisis Leadership of Major Health System Radiology Departments during COVID-19.

Severe acute respiratory syndrome coronavirus 2 has spread across the world since December 2019, infecting 100 million and killing millions. The impact on health care institutions during the coronavirus disease 2019 pandemic has been considerable, with exhaustion of institutional and personal protective equipment resources during local outbreaks and crushing financial consequences for many institutions. Establishing adaptive principles of leadership is necessary during crises, fostering quick decision-making and workflow modifications, while a rapid review of data must determine necessary course corrections. This report describes concepts of crisis leadership teams that can help maximize their effectiveness during the current and future pandemics.

RSNA International Trends: A Global Perspective on the COVID-19 Pandemic and Radiology in Late 2020.

The coronavirus disease 2019 pandemic has challenged and changed health care systems around the world. There has been a heterogeneity of disease burden, health care resources, and nonimaging testing availability, both geographically and over time. In parallel, there has been a continued increase in understanding how the disease affects patients, effectiveness of therapeutic options, and factors that modulate transmission risk. In this report, radiology experts in representative countries from around the world share insights gained from local experience. These insights provide a guidepost to help address management challenges as cases continue to rise in many parts of the world and suggest modifications in workflow that are likely to continue after this pandemic subsides.

Randomized Controlled Trial Comparing Drug-coated Balloon Angioplasty versus Conventional Balloon Angioplasty for Treating Below-the-Knee Arteries in Critical Limb Ischemia: The SINGA-PACLI Trial.

Background There is a paucity of randomized trials demonstrating superior efficacy of drug-coated balloon angioplasty (DCBA) compared with conventional percutaneous transluminal angioplasty (PTA) for below-the-knee arterial disease in patients with -critical limb ischemia. Purpose To compare DCBA versus PTA for below-the-knee lesions in participants with critical limb ischemia through 12 months. Materials and Methods In this prospective, randomized, two-center, double-blind superiority study, participants with critical limb ischemia with rest pain or tissue loss with atherosclerotic disease in the native below-the-knee arteries were randomly assigned (in a one-to-one ratio) to DCBA or PTA after stratification for diabetes and renal failure between November 2013 and October 2017. The primary efficacy end point was angiographic primary patency at 6 months analyzed on an intention-to-treat basis. Secondary end points through 12 months were composed of major adverse events including death and major amputations, wound healing, limb salvage, clinically driven target-lesion revascularization, and amputation-free survival. Primary and binary secondary end points, analyzed by using generalized-linear model and time-to-event analyses, were estimated with Kaplan-Meier survival curves and hazard ratios (Cox regression). Results Seventy participants (mean age, 61 years ± 10 [standard deviation]; 43 men) in the DCBA group and 68 (mean age, 64 years ± 10; 50 men) in the PTA group were evaluated. The percentage of patients with angiographic primary patency at 6 months was 43% (30 of 70) in the DCBA group and 38% (26 of 68) in the PTA group (P = .48). Through 12 months, the percentage of deaths was similar: 21% in the DCBA group and 16% in the PTA group (P = .43). Amputation-free survival rate assessed with Kaplan-Meier curves differed through 12 months: 59% (41 of 70) in the DCBA group compared with 78% (53 of 68) in the PTA group (P = .01). Conclusion In participants with critical limb ischemia, the drug-coated balloon angioplasty group and the conventional percutaneous transluminal angioplasty group had similar primary patency rates at 6 months after treatment of below-the-knee arteries. Amputation-free survival rates through 12 months were higher in the percutaneous transluminal angioplasty group. © RSNA, 2021 Online supplemental material is available for this article.